I've noticed that models that have a lot of open bays (i.e. just covered with Monokote or somethign) make a lot of noise from vibration. Might do a soft mount for my upcoming 40 size project if I had an easy, cheap way to do it.

I am playing with the idea of making a large, light wooden muffler built into the fuselage so it's larger and less ugly.

My Scooter 2 had an FP40 with 11" instead of 10" prop, and the optional baffles and extension for the muffler. Couldn't hear it if other people were up. I've got to think if homework is done on the LA 15 and soft mount is used it could be made almost arbitrarily quiet without going to diesel or electric